Issue #15610: The PyImport_ImportModuleEx macro now calls

PyImport_ImportModuleLevel() with a 'level' of 0 instead of -1 as the
latter is no longer a valid value.

Also added a versionchanged note for PyImport_ImportModuleLevel() just
in case people don't make the connection between changes to
__import__() and this C function.

Doc/c-api/import.rst

@@ -44,8 +44,7 @@ Importing Modules
    .. index:: builtin: __import__
 
    Import a module.  This is best described by referring to the built-in Python
-   function :func:`__import__`, as the standard :func:`__import__` function calls
-   this function directly.
+   function :func:`__import__`.
 
    The return value is a new reference to the imported module or top-level
    package, or *NULL* with an exception set on failure.  Like for
@@ -76,6 +75,9 @@ Importing Modules
    Similar to :c:func:`PyImport_ImportModuleLevelObject`, but the name is an
    UTF-8 encoded string instead of a Unicode object.
 
+   .. versionchanged:: 3.3
+         Negative values for **level** are no longer accepted.
+
 .. c:function:: PyObject* PyImport_Import(PyObject *name)
 
    This is a higher-level interface that calls the current "import hook